Four pinion differential with cross pin retention unit and related method

ABSTRACT

A differential having four pinions supported for rotation on cross pins within a differential case. The differential employs a retainer system for securing the cross pins relative to the differential case. The retainer system can include a collar and a plurality of pin members.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/975,613, entitled FOUR PINION DIFFERENTIAL WITHCROSS PIN RETENTION UNIT AND RELATED METHOD, and filed Sep. 27, 2007.The disclosure of the aforementioned patent application is herebyincorporated by reference as if fully set forth in its entirety herein.

FIELD OF THE INVENTION

The present disclosure generally relates to vehicle drivelines and moreparticularly to a differential for a vehicle driveline.

One type of automotive differential employs a differential housing, apair of bevel side gears and a plurality of bevel pinions. Someapplication employ a single pair of bevel pinions that are meshinglyengaged with the bevel side gears and supported for rotation in thedifferential housing about an axis via a single pinion shaft. Vehicledifferentials configured for heavier duty applications typically employtwo pair of bevel pinions that are meshingly engaged with the bevel sidegears. A first pair of the bevel pinions are supported for rotationabout a first pinion axis by a first pinion shaft, while a second pairof the bevel pinions are supported about a second pinion axis by asecond pinion shaft. In some heavy duty differentials, the first andsecond pinion shafts are part of a unitarily formed cross-shapedstructure. Some other heavy duty differentials employ a configuration inwhich an aperture or notch is formed in one or both of the first andsecond pinion shafts. The aperture or notch in one of the first andsecond pinion shafts provides clearance for the other one of the firstand second pinion shaft. Still other heavy duty differentials employ aconfiguration in which the second pinion shaft is formed by two shaftmembers that terminate proximate the first pinion shaft. Examples ofthis configuration include certain models of the TracRite® differentialthat are commercially available from American Axle & Manufacturing,Inc., Detroit, Mich. and U.S. Pat. No. 7,155,997, the disclosure ofwhich is hereby incorporated by reference as if fully set forth indetail herein.

While such configurations are relatively robust, the coupling of thefirst and second pinion shafts to the differential housing can becomplex and/or costly. Accordingly, there remains a need in the art foran improved heavy duty differential having multiple pinion shafts thatcan be robustly secured relative to the differential housing in arelatively simple, efficient and cost-effective manner.

SUMMARY OF THE INVENTION

In one form, the present teachings provide a differential for anautomotive driveline. The differential includes a differential housing,first and second bevel side gears, a first pinion shaft, a first set ofbevel pinions, a second set of bevel pinions and a retainer assembly.The differential housing defines an internal cavity, an axle bore andfirst and second pinion bores. The axle bore is disposed through thedifferential housing and intersects the internal cavity. The axle boreis disposed about a rotational axis of the differential housing. Thefirst and second pinion bores are perpendicular to one another andperpendicular to the rotational axis. The first and second bevel sidegears are received in the internal cavity and disposed about therotational axis. The first pinion shaft is received in the first pinionbore and coupled to the differential housing. The first set of bevelpinions are rotatably disposed on the first pinion shaft and meshinglyengaged with the first and second bevel side gears. The second set ofbevel pinions is meshingly engaged with the first and second bevel sidegears. The retainer assembly is received in the second pinion bore andsupports the second set of bevel pinions for rotation thereon. Theretainer assembly includes a collar, first and second pin portions and aplurality of pin members. The collar is an annular structure that isdisposed about the rotational axis radially inwardly of the first andsecond sets of bevel pinions. The collar has a first set of collarapertures, a second set of collar apertures, a first pin memberaperture, and a pair of second pin member apertures. The first pinmember aperture is formed transverse to and intersects the first set ofcollar apertures. The second pair of pin member apertures are spacedapart from one another and are formed transverse to and intersect thesecond set of pin member apertures. The first pinion shaft is receivedthrough the first set of collar apertures. The first pin portion isreceived in a first side of the second pinion bore, a first one of thesecond set of bevel pinions and the second set of collar apertures. Thesecond pin portion is received in a second side of the second pin bore,a second one of the second set of bevel pinions and the second set ofcollar apertures. The first pin member is received into the first pinmember aperture and a hole formed in the first pinion shaft. The secondpin members are received into respective ones of the second pin memberapertures and respective holes formed in the first and second pinportions.

In another form, the present teachings provide a method for assemblingan automotive differential. The method includes: providing adifferential case having an internal cavity; installing a first bevelside gear into the internal cavity for rotation about a rotational axis;meshingly engaging a first set of bevel pinions to the first bevel sidegear for rotation about a first pinion axis; meshingly engaging a secondset of bevel pinions to the first bevel side gear for rotation about asecond pinion axis; positioning a collar in the internal cavity radiallyinwardly of the first and second sets of bevel pinions; installing firstand second pin portions to the first set of bevel pinions, each of thefirst and second pin portions extending through the collar, through anassociated one of the first set of bevel pinions and engaging thedifferential case; installing a first pinion shaft to the second set ofbevel pinions, the first pinion shaft extending through the collar andthe second set of bevel pinions, the first pinion shaft having oppositeends that engage the differential case; installing a first pin memberthrough the collar and the first pinion shaft; installing a second pinmember through the collar and the first pin portion; and installing athird pin member through the collar and the second pin portion.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of an exemplary vehicle having adifferential unit constructed in accordance with the teachings of thepresent disclosure;

FIG. 2 is a partially broken away perspective view of a portion of thevehicle of FIG. 1 illustrating the rear axle assembly in more detail;

FIG. 3 is a sectional view of a portion of the vehicle of FIG. 1,illustrating the differential unit in longitudinal cross section;

FIG. 4 is a sectional view taken along the line 4-4;

FIG. 5 is an enlarged portion of FIG. 4, illustrating a portion of thedifferential unit where the first and second pin portions abut the firstpinion shaft.

FIGS. 6 and 7 are similar to FIG. 5 but illustrate different endconditions of the first and second pin portions;

FIG. 8 is a sectional view similar to FIG. 3, but illustrating anotherdifferential unit constructed in accordance with the teachings of thepresent disclosure;

FIG. 9 is a perspective view of a portion of the differential unit ofFIG. 8; and

FIG. 10 is a sectional view of a portion of another differentialconstructed in accordance with the teachings of the present disclosure,the sectional view being taken longitudinally through the first andsecond pin portions and the first pinion shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 of the drawings, a vehicle having adifferential assembly that is constructed in accordance with theteachings of the present disclosure is generally indicated by referencenumeral 10. The vehicle 10 can include a driveline 12 that is drivablevia a connection to a power train 14. The power train 14 can include anengine 16 and a transmission 18. The driveline 12 can include a driveshaft 20, a rear axle 22 and a plurality of wheels 24. The engine 16 canbe mounted in an in-line or longitudinal orientation along the axis ofthe vehicle 10 and its output can be selectively coupled via aconventional clutch to the input of the transmission 18 to transmitrotary power (i.e., drive torque) therebetween. The input of thetransmission 18 can be commonly aligned with the output of the engine 16for rotation about a rotary axis. The transmission 18 can also includean output and a gear reduction unit. The gear reduction unit can beoperable for coupling the transmission input to the transmission outputat a predetermined gear speed ratio. The drive shaft 20 can be coupledfor rotation with the output of the transmission 18. Drive torque can betransmitted through the drive shaft 20 to the rear axle 22 where it canbe selectively apportion in a predetermined manner to the left and rightrear wheels 24 a and 24 b, respectively.

With additional reference to FIG. 2, the rear axle 22 can include adifferential assembly 30, a left axle shaft assembly 32 and a right axleshaft assembly 34. The differential assembly 30 can include a housing40, a differential unit 42, an input pinion 44 and a ring gear 46. Thehousing 40 can support the differential unit 42 for rotation about afirst axis 48 and can further support the input pinion 44 for rotationabout a second axis 50 that can be perpendicular to the first axis 48.

The housing 40 can be initially formed in a suitable casting process andthereafter machined as required. The housing 40 can include a wallmember 52 that can define a central cavity 54 having a left axleaperture 56, a right axle aperture 58, and an input shaft aperture 60.

The left axle shaft assembly 32 can include a first axle tube 62 fixedto the left axle aperture 56 and a first axle half-shaft 64 that can besupported for rotation in the first axle tube 62 about the first axis48. Similarly, the right axle shaft assembly 34 can include a secondaxle tube 66 that can be fixed to the right axle aperture 58 and whichcan support a second axle half-shaft 68 for rotation about the firstaxis 48.

The input pinion 44 can be disposed in the input shaft aperture 60 andcan meshingly engage the ring gear 46, which can be fixedly butremovably coupled to the differential unit 42. It will be appreciatedthat rotary power transmitted to the input pinion 44 from the driveshaft 20 is employed to drive the differential unit 42 about the firstaxis 48 via the ring gear 46 in a conventional manner. The differentialunit 42 can transmit drive torque to the first and second axlehalf-shafts 64 and 68 in a predetermined manner.

With additional reference to FIGS. 3 and 4, the differential unit 42 canbe disposed within the central cavity 54 of the housing 40 and caninclude a differential housing 100, first and second bevel side gears102 and 104, respectively, a first set of bevel pinions 106, a secondset of bevel pinions 108, a first pinion shaft 110 and a retainer system112.

The differential housing 100 can include a differential case 120 and adifferential cover 122. The differential case 120 can have a body 126and a flange 128 that can be disposed generally perpendicular to therotational axis 48 a of the differential unit 42. The body 126 candefine an internal cavity 130, a first axle bore 132, a first pinionshaft bore 134 and a second pinion shaft bore 136. The first axle bore132 can be disposed about the rotational axis 48 a of the differentialunit 42 and can intersect the internal cavity 130 on an end of the body126 opposite the flange 128. The first pinion shaft bore 134 can extendthrough the body 126 along a first pinion axis 144 that is generallyperpendicular to the rotational axis 48 a of the differential unit 42.The second pinion shaft bore 136 can extend through the body 126 along asecond pinion axis 146 that is generally perpendicular to both therotational axis 48 a of the differential unit 42 and the first pinionaxis 144. The differential cover 122 can be coupled to the differentialcase 120 to substantially close an end of the differential case 120opposite the first axle bore 132. The differential cover 122 can definea second axle bore 152 that can be arranged about the rotational axis 48a of the differential unit 42. The first and second axle bores 132 and152 can be sized and shaped to engage an end of an associated one of thefirst and second axle half-shafts 64 and 68 (FIG. 2) in a conventionalmanner that permits drive torque to be transmitted between thedifferential housing 100 and the first and second axle half shafts 64and 68 (FIG. 2).

The first and second bevel side gears 102 and 104 can be conventional intheir construction and as such, need not be discussed in significantdetail herein. Briefly, the first and second bevel side gears 102 and104 can include a plurality of gear teeth 160 and a central splinedaperture 162 that is configured to non-rotatably but axially slide-ablyengage a corresponding one of the first and second axle half shafts 64and 68 (FIG. 2) to permit drive torque to be transmitted between thefirst and second bevel side gears 102 and 104 and the first and secondaxle half shafts 64 and 68 (FIG. 2). The first and second bevel sidegears 102 and 104 can be received in the internal cavity 130 on oppositesides of the differential case 120 such that they are aligned about therotational axis 48 a of the differential unit 42 and abutted against thedifferential case 120 and the differential cover 122, respectively.

The first and second sets of bevel pinions 106 and 108 can be can beconventional in their construction and as such, need not be discussed insignificant detail herein. Briefly, the first and second sets of bevelpinions 106 and 108 can include gear teeth 170 that can meshingly engagethe first and second bevel side gears 102 and 104, a surface 172opposite the gear teeth 170 that can be configured to engage thedifferential case 120, and a through bore 174. In the particular exampleprovided, the opposite surface 172 is arcuate in shape and conforms tothe arcuate recesses 176 that are formed in the internal cavity 130 ofthe differential case 120 at the locations where the first and secondpinion shaft bores 134 and 136 intersect the interior side of the wallof the differential case 120. The first set of bevel pinions 106 caninclude a first pinion 106 a and a second pinion 106 b that can bereceived in the arcuate recesses 176 that are associated with the firstpinion shaft bore 134. The second set of bevel pinions 108 can include afirst pinion 108 a and a second pinion 108 b that can be received in thearcuate recesses 176 that are associated with the second pinion shaftbore 136.

The first pinion shaft 110 can be received in the first pinion shaftbore 134 and through the through bores 174 in the first and secondpinions 106 a and 106 b of the first set of bevel pinions 106.

The retainer system 112 can include a second pinion shaft 200, a collar202 and a plurality of pin members 204. The second pinion shaft 200 cansupport the second set of bevel pinions 108 for rotation in the internalcavity 130 about the second pinion axis 146. The second pinion shaft 200can include a first pin portion 210 on which the first pinion 108 a isrotatably disposed, and a second pin portion 212 on which the secondpinion 108 b is rotatably disposed. The first and second pin portions210 and 212 can be received in the second pinion shaft bore 136 alongthe second pinion axis 146. In the particular example provided, thefirst and second pin portions 210 and 212 are discretecylindrically-shaped members having inner ends 214 that are generallyflat and orthorgonal to the second pinion axis 146 as shown in FIG. 5.It will be appreciated, however, that the first and second pin portions210 and 212 could have inner ends 214 that conform to a shape of atleast a portion of the first pinion shaft 110, an example of which isshown in FIG. 6 or engage one or more holes 216 that can be formed inthe first pinion shaft 110 as shown in FIG. 7.

Returning to FIGS. 3 and 4, the collar 202 can be disposed in theinternal cavity 130 radially inward of the first and second sets ofbevel pinions 106 and 108. The collar 202 can be an annular structurehaving a first set of apertures 230, which can be sized to receive thefirst pinion shaft 110 therethrough, and a second set of apertures 232that are sized to receive the first and second pin portions 210 and 212therethough. Accordingly, it will be appreciated that the collar 202supports the first and second pin portions 210 and 212 on a sideopposite the wall of the differential case 120. The collar 202 can havea width that can be sufficient to fully support the first pinion shaft110 and/or the first and second pin portions 210 and 212 (i.e., theouter ends of the first pinion shaft 110 and/or the outer ends of thefirst and second pin portions 210 and 212 need not engage thedifferential case 120).

The pin members 204 can include a first set of pin members 260 and asecond set of pin members 262. While the first and second sets of pinmembers 260 and 262 can be any type of pins, roll pins are employed inthe example illustrated. The first set of pin members 260 can bereceived through holes 270 formed through the collar 202 and holes 272formed through the first pinion shaft 110. In the example provided, thefirst set of pin members 260 includes a pair of pin members, but it willbe appreciated that the first set of pin members 260 could include asingle pin member. The second set of pin members 262 can be receivedthrough holes 274 formed through the collar 202 and holes 276 formedthrough the first and second pin portions 210 and 212.

The first and second sets of pin members 260 and 262 can be installed tothe holes 270 and 274, respectively, and the holes 272 and 276,respectively, in a direction that can be generally parallel to therotational axis 48 a of the differential unit 42. Accordingly, it willbe appreciated that the first and second pinion shafts 110 and 200 canbe secured to one another in a cost-efficient manner.

While the retainer system 112 has been illustrated and described hereinas including a plurality of discrete pin members, it will be appreciatedthat a differential constructed in accordance with the teachings of thepresent disclosure could be constructed somewhat differently. Forexample, the retainer system 112 a could include a plate member 320 towhich one or more of the pin members 204 a can be coupled as shown inFIGS. 8 and 9. The pin members 204 a can be coupled to the plate member320 in any appropriate manner, such as press-fit, welded (e.g., frictionwelded, resistance welded) or integrally formed with the plate member320. One or more of the pin members 204 a can include a protrusion, suchas a tab or circumferentially-extending rib or bead 322 that can besized to frictionally engage the collar 202 a on a side opposite thefirst pinion shaft 110 and/or the first and second pin portions 210 and212 to thereby resist withdrawal of the pin member(s) 204 a from thecollar 202 a.

In the example of FIG. 10, the first pinion shaft 110 b is relativelylarger in diameter than the second pinion shaft 200 b. An aperture 400can be formed through the first pinion shaft 110 b through which thesecond pinion shaft 200 b can extend. Configuration in this mannerpermits the first and second pin portions (not specifically shown) to bea part of a unitary structure.

While the invention has been described in the specification andillustrated in the drawings with reference to a preferred embodiment, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment illustrated by the drawingsand described in the specification as the best mode presentlycontemplated for carrying out this invention, but that the inventionwill include any embodiments falling within the foregoing descriptionand the appended claims.

1. A differential for an automotive driveline, the differentialcomprising: a differential housing defining an internal cavity, an axlebore and first and second pinion bores, the axle bore being disposedthrough the differential housing and intersecting the internal cavity,the axle bore being disposed about a rotational axis of the differentialhousing, the first and second pinion bores being perpendicular to oneanother and perpendicular to the rotational axis; first and second bevelside gears received in the internal cavity and disposed about therotational axis; a first pinion shaft received in the first pinion boreand coupled to the differential housing; a first set of bevel pinionsrotatably disposed on the first pinion shaft and meshingly engaged withthe first and second bevel side gears; a second set of bevel pinionsmeshingly engaged with the first and second bevel side gears; and aretainer assembly received in the second pinion bore and supporting thesecond set of bevel pinions for rotation thereon, the retainer assemblyincluding a collar, first and second pin portions and a plurality of pinmembers, the collar being an annular structure that is disposed aboutthe rotational axis radially inwardly of the first and second sets ofbevel pinions, the collar having a first set of collar apertures, asecond set of collar apertures, a first pin member aperture, and a pairof second pin member apertures, the first pin member aperture beingformed transverse to and intersecting the first set of collar apertures,the second pair of pin member apertures being spaced apart from oneanother and being formed transverse to and intersecting the second setof pin member apertures, the first pinion shaft being received throughthe first set of collar apertures, the first pin portion being receivedin a first side of the second pinion bore, a first one of the second setof bevel pinions and the second set of collar apertures, the second pinportion being received in a second side of the second pin bore, a secondone of the second set of bevel pinions and the second set of collarapertures, the first pin member being received into the first pin memberaperture and a hole formed in the first pinion shaft, the second pinmembers being received into respective ones of the second pin memberapertures and respective holes formed in the first and second pinportions.
 2. The differential of claim 1, wherein at least one of thefirst and second pin members comprises a plurality of roll pins.
 3. Thedifferential of claim 1, wherein at least one of the first and secondpin members frictionally engages at least one of the first pin portion,the second pin portion and the first pinion shaft.
 4. The differentialof claim 1, wherein the first and second pin portions are discretestructures.
 5. The differential of claim 4, wherein each of the firstand second pin portions has an inner end that is disposed adjacent thefirst pinion shaft and wherein the inner end has an surface that issubstantially parallel to the rotational axis of the differentialhousing.
 6. The differential of claim 4, wherein each of the first andsecond pin portions has an inner end that is disposed adjacent the firstpinion shaft and wherein the inner end has an surface that at leastpartially conforms to a corresponding portion of a surface of the firstpinion shaft.
 7. The differential of claim 6, wherein the correspondingportion of the surface of the first pinion shaft is cylindricallyshaped.
 8. The differential of claim 1, wherein the holes in the firstpinion shaft and the holes in the first and second pin portions aredisposed generally parallel to the rotational axis of the differentialhousing.
 9. The differential of claim 1, wherein the second pin membersare coupled to a plate member that abuts the collar.
 10. Thedifferential of claim 9, wherein the first pin member is coupled to theplate member.
 11. The differential of claim 10, wherein at least one ofthe first and second pin members carries a feature that engages thecollar to resist withdrawal of the at least one of the first and secondpin members from the collar.
 12. The differential of claim 1, wherein atleast one of the first and second pin members carries a feature thatengages the collar to resist withdrawal of the at least one of the firstand second pin members from the collar.
 13. The differential of claim 1,wherein the first and second pin portions are formed on a second pinionshaft.
 14. The differential of claim 13, wherein the first and secondpin portions are formed on a second pinion shaft.
 15. The differentialof claim 14, wherein the first pinion shaft has an aperture throughwhich the second pinion shaft extends through.
 16. A method forassembling an automotive differential, the method comprising: providinga differential case having an internal cavity; installing a first bevelside gear into the internal cavity for rotation about a rotational axis;meshingly engaging a first set of bevel pinions to the first bevel sidegear for rotation about a first pinion axis; meshingly engaging a secondset of bevel pinions to the first bevel side gear for rotation about asecond pinion axis; positioning a collar in the internal cavity radiallyinwardly of the first and second sets of bevel pinions; installing firstand second pin portions to the first set of bevel pinions, each of thefirst and second pin portions extending through the collar, through anassociated one of the first set of bevel pinions and engaging thedifferential case; installing a first pinion shaft to the second set ofbevel pinions, the first pinion shaft extending through the collar andthe second set of bevel pinions, the first pinion shaft having oppositeends that engage the differential case; and installing a first pinmember through the collar and the first pinion shaft; installing asecond pin member through the collar and the first pin portion; andinstalling a third pin member through the collar and the second pinportion.
 17. The method for assembling the automotive differential ofclaim 16, wherein at least one of the first, second and third pinmembers is a roll pin.
 18. The method for assembling the automotivedifferential of claim 16, wherein the first, second and third pinmembers are disposed generally parallel to the rotational axis.
 19. Themethod for assembling the automotive differential of claim 16, whereinat least two of the first, second and third pin members are coupled to aplate member.
 20. The method of claim 19, wherein the at least two ofthe first, second and third pin members and the plate member areunitarily formed.